Help with dying Glofish

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Aquarium Advice Newbie
Mar 10, 2023
Hello! My family and I are new to the fish world and we are so far having terrible luck. My 8 year old wanted fish for Christmas so we got her a brand new tank and all the accessories and on the 27th of December bought 4 glofish from Petco.

They did amazing for 2 months till one day one was swimming sideways and within 24 hours all four were dead. We waited a few weeks. Emptied and throughly rinsed everything from the tank. Filled it and treated the water, new filter etc. added a bubbler. Waited a week and took a water sample to the fish shop and the water was perfect. Waited another few days before bringing home 4 new glofish this past Sunday.

It’s not even been a week. This morning one of them is swimming sideways and struggling just like it started with the others. Our home test strips are showing water levels are fine. I called the fish shop we got them from and they weren’t very helpful at all which was frustrating. We’ve only been feeding them every other day since we are wondering if over feeding is what killed the others.

Any thoughts and advice would be very appreciated. Wondering if we need to just go a different fish route and move on from glofish.
You havent cycled the tank.

What do you understand about the nitrogen cycle? Do you know how to cycle a tank? I assume you dont have a water test kit?

How big is the tank? Does it have a heater and filter?

For now, get a cupful of water from your tank to test later, then change 50% of the water. Either get a water test kit that tests for pH, ammonia, nitrite and nitrate, or take the sample to the fish store and get them to test for you. Write down the test results and let us know the numbers. Get a test kit as soon as you are able, preferably a liquid test kit. API Freshwater Master Test Kit is a good one to go for.

Until you are able to test the water, change 30 to 50% everyday.

Here is a link to a page of useful articles for new fish keepers.
A little more on the advice the store gave you about your water.

Fish store employees often know no more about keeping fish than you do. They rarely know about cycling a tank, and even more rarely pass useful information on about how to do this.

They tested your water and said everything is good. But all a water test will tell you if the safe at the time the sample of water was removed. It will tell you nothing about whether the tank is properly established to keep the water safe going forward. This establishing is called cycling. There are processes on how to do this and these processes typically take a couple of months.

Just picked up you have test strips. While these are considered not accurate or reliable, can you post the results you have from them.
Like mentioned I’d also have to say this is a water quality issue. Unfortunately most pet shops don’t care or even the employees don’t know how to properly set up a tank. In the end it usually end up like this unfortunately

Please read the links Aiken posted and get familiar with the nitrogen cycle, what to test, how to test and all that fun stuff. Unfortunately fish keeping isn’t just buying a tank and plopping some fish in there. But with proper knowledge it can be just about that easy, it just takes some time to get the tank ready.

I would suggest getting a liquid test kit, they aren’t overly expensive and last for quite a while. And imo are more accurate than most strips, you’ll be using them a lot more often within the first few months until the tank finds its happy place then you’ll still want to at least do a weekly test on the tank to make sure nothing weird is going on!

There’s 2 ways to go about cycling the tank. Fishless or fish-in. Fishless poses no risk to any fish of course but typically takes a lot longer and sometimes just never does establish a cycle. Fish-in is a lot more hands-on, you need to be monitoring water quality closely and feeding sparingly as there is a fairly fine line between being safe for the fish and having enough ammonia in the tank to start the nitrogen cycle. I’m a big fan of just doing fish-in cycles and I’m sure your kid would be too, because who wants to stare at an empty box of water for 2 months?

Depending on the size of the tank, even if you have to start with only one fish until the tank cycles is still better than a box of water! Lol. Once you see the nitrogen cycle progress to only nitrates in the water you can chose to either feed more or add another fish or 2. Just keep in mind that a new tank needs time for the bacteria to establish a sufficient colony. If you see the nitrogen cycle is established and go and throw a handful of fish in there and start feeding more you will likely overcome the bacteria and start seeing ammonia and nitrite spikes. It’s a delicate process off the start but as the tank “seasons” it will be a lot less susceptible to water quality fluctuations
Hi and welcome to the forum :)

Do you have any pictures of the fish (dead or alive)?
Can you post a picture of the entire aquarium?

Can you post a picture of the test strip next to the colour chart so we can see the actual colours/ numbers?

If you get water tested by a pet shop, write the results down in numbers at the time they do the test. If the shop says the water is fine, ask them for the numbers.

How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the aquarium?

Do you have buckets and hoses specifically for the fish tank?

What sort of filter is on the tank?
How often and how do you clean the filter?


If most or all of the fish die in a short space of time, it's usually poisoning. This can be from a new filter that hasn't developed the beneficial bacteria to keep ammonia and nitrite at 0ppm, or poison from an external source (cream, oil, perfume, hand sanitiser, moisturiser, perfume from soap, cigarette smoke, etc). If the water has 0ppm of ammonia and 0ppm nitrite, then it's a poison getting into the aquarium.

Did anyone do anything to the tank on the day before the fish died or in the morning when they died?

Does anyone in the house use perfumes, deodorants, smoke, paint or do anything that releases fumes in the room or near the fish tank?

Do you wash your hands with soap before working in the tank?
If yes, does the soap have a perfume in it?

I'm assuming the aquarium is in your child's room. Do they put anything in the tank (fingers, toys, anything)?
I know that everything is probably overwhelming right now. It’s never fun having to tell your kiddos about the fish disappearing.

How many gallons is the tank and what fish are they? You shouldn’t add any fish to a tank that isn’t cycled yet. You have to add the water and set the tank up while adding water conditioner and letting your tank filter. It can take up to weeks depending on how big the tank is. I would suggest going to the store and getting a Quick Start which can promote your tank to be cycled quicker but that may be the reason your fish are dying.

Also you should research the appropriate water parameters for your fish beforehand because they may be dying due to water parameters. If the tank is small then the fish can be dying due to it being crowded. If you are feeding the fish too often and too much then they can be dying due to over feeding.

A lot of factors contribute to why your fish are passing. Fish from main chain stores tend to be interbred and have issues such as diseases and parasites. I would suggest buying your fish from breeders and/or checking out small fish shop locations.

I would say to move on from glofish and find other fish.
Check out Neon Tetras, Rasboras, and other fish that are beginner friendly and easy to take care of. They are very colorful and vibrant.

I would also suggest adding live plants if you don’t have any. Plants help recycle nitrates and nitrites in your water. Safely wash them before adding them so you don’t have a snail pest problem. This can promote a lot in your tank. There are also things you can add for beneficial bacteria to grow which can help your tank as well.

Happy fishing! ��
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